Vacuum photographic printing apparatus



March 27, 1956 E. w. HOSTERMAN 2,73

VACUUM PHOTOGRAPHIC PRINTING APPARATUS Filed May 13, 1952 5 Sheets-Sheet l N O a a h 11142!!! an: 55 A 2 q I EENTOR.

\1 5EARL w. HOSTERMAN ATTOR EYS March 27', 1956 E. w. HOSTERMAN 2,739,516

VACUUM PHOTOGRAPHIC PRINTING APPARATUS Filed May 13, 1952 5 Sheets-Sheet 2 7 INVENTOR. EARL W. HOSTERMAN ATTORNEYS March 27, 1956 s. w. HOSTERMAN 2,739,516

VACUUM PHOTOGRAPHIC PRINTING APPARATUS Filed May 13, 1952 5 Sheets-Sheet 4 B3 2.39 m A m m a \\w\ m M v ww E\\ k T on m m 7 m ow 2.. T mum wl mm N I I a 8 m mm m Q 0& IMW On V. mv B v9 x x 7, x 7, x 5 NN v A q I mm mm Q mm mm 5 n 3 3 S Q m 8 no. w .I Q w 5 mv on mm m @E a v 8 M mv March 27, 1956 E. w. HOSTERMAN VACUUM PHOTOGRAPHIC PRINTING APPARATUS 5 Sheets-Sheet 5 Filed May 15, 1952 M OM INVENTOR. EARL W. HOSTERMAN BY l w wE

ATTORNEYS United States Patent VACUUM PHOTOGRAPHIC PRINTING APPARATUS Earl W. Hosterman, Cuyahoga Falls, Ohio, assignor to The Morse Instrument Company, Hudson, Ohio, a corporation of Ohio Application May 13, 1952, Serial No. 287,467

7 Claims. (Cl. 95-76) The invention relates generally to contact printers for making high definition pictures from high definition negatives with a diffusion light source, and a primary object is to provide a novel contact printing apparatus using vacuum to obtain perfect and overall contact between relatively large negatives and photographic paper or film so as to obtain perfect definition in the finished print.

In making prints on a contact printer with a diffusion light source, the negative and printing paper are pressed fiat against a printing glass and any minute spaces between the negative and printing paper cause the fine details of the image to become blurred in the final print. Such spaces are usually created by the inclusion of air bubbles trapped between the negative and the printing paper, and these bubbles, once they are trapped, are practically impossible to remove by increasing pressure on the prints because the increased pressure tends to form a seal around the bubbles.

In small size conventional contact printers, the air bubbles can be satisfactorily removed by using an inflated pneumatic rubber platen with a convex surface to press the printing paper and negative against the printing glass. Due to the convex platen, the center of the printing area is contacted first and the contact area is progressively increased from the center outwardly, so that the air bubbles are rolled or pushed to the outer edges without being trapped. However, where the size of the printing area is relatively large, for example greater than an area of about 9" x 18", the pressure exerted by the convex platen requires a printing glass of impractical thickness in order to prevent breakage, and this, together with the large bulk of the convex platen necessitating that it be power operated, makes the size and weight of the printing unit excessive and its cost impracticable, if not prohibitive.

Certain prior contact printers have employed means for creating a vacuum between the printing platen and the printing glass in order to increase the unit pressures between the negative and printing paper and still preclude the printing glass from being subjected to destructive force. In certain of these vacuum contact printers the printing platen is a flexible diaphragm of rubber or the like which is pressed aaginst the printing glass by atmospheric pressure when a vacuum is created between the platen and the glass. However, when such a diaphragm is flexed against the printing glass, with the negative and printing paper in between, there is nothing to prevent the entrapment of minute air bubbles between the negative and printing paper.

If a single point light source, such as an electric arc, is used in these prior vacuum printers, fairly good results can be obtained with pictures not requiring high definition even though some air bubbles are still entrapped during the printing operation. However, when a diffusion light source is used for making high definition pictures, the light strikes every point of the image from all directions and the most minute air bubbles will cause "ice blurring with consequent loss of definition. To meet the requirements of high definition pictures with prior contact printers using vacuum, therefore, it is necessary to allow the platen to remain under vacuum as long as 15 minutes to be sure all the air bubbles are removed from between the negative and printing paper.

In prior contact printers using vacuum, it is important to provide a compressible sealing gasket of rubber or the like around the margins of the printing glass and platen so that a good vacuum can be maintained therebetween. Such gasket provides a seal of limited width and tends to produce leaks at the joint or joints between the abutting ends of the gasket, and also, if printing on film is being done, leaks occur along the edges of a strip of film passing from a film spool on the exterior of the printer under the gasket and into the space between the printing glass and platen.

A specific object of the present invention is to provide a novel vacuum printing apparatus which will obtain substantially perfect overall contact between a relatively large negative and the printing medium without subjecting the printing glass to destructive force.

Another object is to provide a novel vacuum printing apparatus which will eliminate the need for a pneumatic convex printing platen and reduce the bulk and cost of the apparatus to a minimum.

A further object is to provide a novel vacuum printing apparatus which removes all air between the negative and printing medium to provide perfect overall contact in a minimum period of time in advance of the printing operation.

A still further object is to provide a novel vacuum printing apparatus which provides a wide continuous seal around the margin of the printing glass, enabling passing a strip of film into the space between the printing glass and platen without material loss of vacuum.

Finally, it is an object to provide a novel vacuum contact printing apparatus using a diffusion light source for obtaining high definition, large size pictures, which apparatus accomplishes the foregoing purposes and over comes the difficulties and disadvantages of the prior art.

A preferred embodiment of the present invention is shown by way of example and described herein, but it is to be understood that various modifications and improvements may be made without departing from the scope of the invention as defined in the appended claims. Referring to the drawings:

Fig. l is a side elevation of the novel printing apparatus, showing the cover in released slightly ajar position;

Fig. 2 is a plan sectional view, somewhat schematic, as on line 22, Fig. 1;

Fig. 3 is a plan view, partly broken away, of the cover with its top plate removed;

Fig. 4- is an enlarged fragmentary sectional view as on line 44, Fig. 3;

Fig. 5 is an enlarged fragmentary sectional view, as on line 5-5, Fig. 3;

Fig. 6 is an enlarged fragmentary sectional view as on line 66, Fig. 3;

Fig. 7 is a view similar to Fig. 6, showing the position of the platen and diaphragm during printing; and

Fig. 8 is a diagrammatic view showing the electrical wiring and vacuum system.

Similar numerals refer to similar parts throughout the drawings.

The printing apparatus of the present invention includes a rectangular cabinet indicated generally at 10 in Fig. 1 and having a rectangular cover or lid indicated generally at 11 hinged to the cabinet at its rear edge. Preferably, the hinges include brackets 12 attached to the rear of the cover and connected to hinge arms 13 pivoted at 14 to the upper ends of housings 15 mounted on the rear of the cabinet. Each housing may enclose a well known spring plunger arrangement yieldingly resisting closing movement of the cover. 7

The cabinet 159 includes a suitable frame work having a preferably sheet metal casing including side panels in and front and rear panels 17 and 18. Within the cabinet is an electric lamp compartment which may consist of an open top sliding drawer having a horizontal lamp mounting plate 19 and a front plate carryi w a plurality of manual switches 29 controlling the la )3 21 individually or in banks of three or more as desired. The drawer is provided with pull handles 22, so that by loosening screws 23, the drawer may be pulled out to gain access to the lamps. Immediately above the drawer is a frosted diffusion glass 24 through which light from the lamps 21 must pass before it reaches the pri ""ig glass 25 supported at the top of the cabinet around its marginal edges by a metal frame 26, as shown in Fig. 5, there being a sponge rubber cushioning gasket 27 between the glass 25 and frame 26. The cabinet construction per se forms no part of the present invention.

The cover ll preferably includes marginal frame members which may be tubular and rectangular in cross section as shown in Fig. 5. The front frame member is indicated at 215, the rear member at 2) and the side members at 39, and as shown in Fig. 3, these members may be mitered together at the corners, as by welding. A handle 31 is mounted on the front of frame member 28 and includes a hand grip 32, pivoted at 33 on L-shaped brackets 34- attached to the frame member 2.3. The latch hooks 35 have rearwardly extending arms 36 connected to springs 37 urging the latch hooks into position for engaging under the catch plate 38 (Fig. l).

The latch members 35 are released by lifting upwardly on the hand grip 32 to swing the latch hooks outwardly, and movement of the hand grip in either direction is limited by the toggle spring arrangement comprising the transverse bars 39 and it? with compression springs 41 therebetween, which urges the hand grip to a position above or below the pivot 33.

As shown in Figs. 1 and 3, stop bars .2 may be swingably mounted on the front frame member 23, for holding the cover 11 in a slightly open or ajar position when in vertical position as in Fig. l, or for swinging out of the way to horizontal position as in Pi 3, where they are engaged by rubber bumpers A sheet metal cover plate 44 is attached to the frame members 23, 29 and 3% by screws 45, and a vacuum gauge 46 may be mounted in said cover plate in position to be read from the exterior of the cover 11 when closed.

A platen 48, preferably composed of phenolic plastic material is mounted within the rectangular frame comprising members 28, 29 and lit), the platen being rectangular with its edges spaced slightly inward of the frame members as indicated in Figs. 3 and 5. The platen 48 is suspended along its four edges from four angles 49 having one leg connected to the inner surfaces of the frame members by bolts d, and the other leg supporting the platen by bolts 51. The bolts 51 extend through the platen 48 and have beveled heads countersunk in and supporting clamping bars 52 which extend along the undersides of the marginal edges of the platen. Preferably the edge portions of the platen are recessed on their under sides for receiving the clamping bars 52 as indicated at 53, so that a continuous channel 53a is formed in the diaphragm spaced inwardly of the frame, in which the clamping bars 52 are located. The platen 4-8 is somewhat flexible for a purpose to be described, and may be termed semi-flexible.

A flexible diaphragm 54 of rubber or the like extends under and completely covers the platen 48, and the outer portions of the diaphragm are clamped between the clamping bars 52 and the platen by the bolts 51, there being spacer sleeves 55 on the bolts between the platen and the supporting angles. Between the diaphragm 5 and the underside of the platen a fiat air-diiiusing screen 5a; is floatingly supported on the diaphragm, for a purpose to be described. The diaphragm 5 extend outwardly under resilient tubular sealing HlGklllg or gasket 57 of rubber or the like which extends along and is attached to the undersides of the rectangular frame, and the outer edges portions of the diaphragm are secured to the outer sides of the frame members by bin g strips 58 attached to the frame members by screws 59. The sealing molding preferably has a flange dd which is clamped to the frame mern era by metal strips 61 attached to the bottom wall of the frame by screws 62. By extending the diaphragm outwardly under the sealing molding 57, an unbroken seal is obtained around all four sides of the platen regardless of joints in the sealing molding and the effective width of the sealing surfaces is substantialy in creased.

As shown in Figs. 3 and 5, a vacuum connection is provided at the central portion of the platen with the space or chamber A between the platen and diaphragm 5- in which space the screen 5'5 is locate This connection includes an aperture 63 through the platen and connected by a flanged fitting 64 with an elbow 65. Another vacuum connection is provided near one corner of the platen with the space or chamber A as shown in Figs. 3 and 4, including aperture in the platen connected by fitting 67 to an elbow d. A vacuum connection is provided in another corner of the platen with the channel 53a communicating with the space or chamber B between the diaphragm and printing glass 25. As shown in Fig. 6, this vacuum connection includes registering apertures 6*? in the platen, 79 in the diaphragm, and 71 in the clamping bar 52, the aperture 69 being connected by a flanged fitting 72 with an elbow 7.3.

A conventional vacuum pump 75, driven by an electric motor 76, is located in the bottom part of the cabinet lit, and may be provided with an oiler device indicated at 77 on its suction side for lubricating the pump, and an oil trap 78 on its exhaust side. The suction tube 79 leading to the oiler 77 has an electrically operated solenoid valve 8i) of well known construction in the line. A conventional vacuum switch 81 is connected to the vacuum line at the T 82. The contacts of the vacuum switch 8-1 are normally open at atmospheric pressure and are set to close when the vacuum in the line reaches 20 inches of mercury. The solenoid valve has through ports or connections 83 and which are connected when the valve is energized, and a per open to the atmosphere. Ports 34 and 35 are connected when the valve i deenergized. From the T 32 the vacuum line extends through the rear wall of the cabinet as indicated at 86, and connects with flexible tubing 87 entering the rear side of the cover ll, as shown in Fig. 3.

The electrical conductors for supplying current to the motor 76 and solenoid valve Eli) are contained in a cable 5% leading from a terminal box 39 connected with a source of electrical power (not shown). The cable also carries wires supplying current to a conventional timer device indicated at adapted to actuate a switch after a predetermined period of operation. From the box 8), an electrical cord 91 extends carrying a plug for connection with the electric lamp circuits for the lamps and switches on the sliding drawer in the cabinet. Also a cable cord 93 connects the terminal box to the electrical circuits on the cover lll.

Within the cover the vacuum line 37 connects with a T 94, one side of which is connected to an electrically operated solenoid valve 95 and the other side is connected to a vacuum line 96. The solenoid valve 93 has ports 97 and 98 which are connected when the valve is deenergized for connecting the vacuum line with the elbow 65 of the control vacuum connection with the chamber A. The valve has a port d9 open to the atmosphere and ports 98 and 99 are connected when the valve is energized. A vacuum switch 100 is connected by tubing 101 through elbow 63 with chamber A near one rear corner thereof. The contacts of switch 100 are set to close at about 3 inches of mercury on a vacuum decrease, or in other words as the vacuum in chamber A at orifice 66 approaches atmospheric pressure. The vacuum line 96 connects with a T 102, one side of which is connected by a branch line of flexible tubing 103 to the vacuum gauge 46, and the other side is connected by tubing 104 through the elbow 73 to channel 53a formed in the chamber B preferably in the rear corner opposite to the corner near which orifice 66 is located.

In the operation of the novel printing apparatus, the negative is placed emulsion side up on the printing glass 25, which may be about A; thick, and the printing paper is placed emulsion side down on top of the negative. Then the cover, with the stop bars 42 swung out of the way, is lowered until the seal molding 57 presses the rubber diaphragm against the margin of the printing glass and forms a preliminary seal which is continuous and unbroken because the diaphragm covers the joints in the molding. At this time the chamber or space B between the rubber diaphragm 54 and the printing glass may be substantial as shown in Fig. 6, e. g. A to A". Referring to the diagram in Fig. 8, the electrical wires of the power supply are indicated at 105 and 106, a main switch 107 being provided in line 106 and a printing switch 108 in line 105. The electric lamps 21 are connected across the line in circuit with a timer switch 109 shown in normally closed position when the timer is operating.

To start the printing cycle, assuming the main switch 107 is closed, the printing switch 108 is closed to start the vacuum pump motor and energize solenoid valve 80 through wires 110, 111 and 112, thus connecting the vacuum line 87 through ports 83 and 84 of the valve with the vacuum pump 75, and the vacuum line is connected through branch line 104 with chamber B, and through ports 97 and 98 of solenoid valve 95 with chamber A. As the pump starts to exhaust the air from chambers A and B the rubber diaphragm 54 and diifusion screen 56 will remain in contact with the platen 48, because the pressure in chamber A is equal to or slightly less than that in chamber B due to restrictions in the line and orifices leading to chamber A. Thus the assembly of platen 48, screen 56 and diaphragm 54 may, at this point in the cycle, be considered as a rubber covered platen.

As the pump continues to exhaust air from the chamber B, the atmospheric pressure on the bottom side of the printing glass and the top side of the platen causes them to move toward each other, but the seal molding 57 at the outer edges yieldingly resists or retards this movement, so that the printing glass and printing platen bow inward and first contact each other at their central portions. Continued increase in vacuum in chamber B gradually and progressively increases the area of contact from the center out in all directions, causing a rolling or squeegee action which positively precludes the trapping of air at the central portion of the printing area.

When the vacuum in the chamber B and in the suction line 87 connected thereto reaches inches of mercury, the area of contact has extended substantially to the outer edges of the printing area, or almost to the recessed portions 53 of the platen. As previously mentioned, the contacts of vacuum switch 81 are set to close at 20 inches of mercury, which energizes solenoid valve 95 through wires 111, 113 and 114, connecting chamber A through ports 98 and 99 with the atmosphere. As air enters chamber A the diffusion screen prevents a seal being formed between the edge of orifice 63 and the diaphragm, and forms partially restricted air passageways leading to all parts of the chamber A, starting from the center and moving gradually outward. This augments the rolling or squeegee action previously described occurring between the diaphragm and printing glass and tends to remove any and all final traces of air in said chamber B.

As indicated in Fig. 7, at the end of this progressive squeegee action the atmospheric pressure above and below the platen 48 and below the printing glass causes the platen and the printing glass to return to their normal fiat condition free of stress. The flexible diaphragm is then in perfect and complete contact with the printing glass at the outermost edges of the printing area, even beyond the inner edges of the recessed portions 53 of the platen 48, without relying on the contact of the platen itself. Due to the vacuum maintained in chamber B, the width of seal provided by the outer marginal portion of the diaphragm under the seal molding is substantially increased so as to produce a positive and efiicient seal, even though printing is done on a strip of film passed into the chamber B from the sides of the cabinet. In this connection, Fig. 1 shows an idler roller 115 mounted along one upper side edge of the cabinet for guiding film into chamber B, and film spool brackets 116 and 117 are mounted on the side of the cabinet below the roller.

As the atmospheric air enters chamber A through orifice 63, the vacuum previously created in that chamber is decreased and when the pressure in the chamber reaches about 3 inches of mercury, the contacts of switch 100 close, connecting wires 113 and 118 with timer switch 109, energizing the printing lamps 21 and timer clutch 119 and starting the timer motor 90 to start the printing cycle. At the end of a predetermined period of time, the timer motor opens switch 109 and shuts off the .7 printing lamps. The printing switch 103 is then manually opened and the whole system is tie-energized. De-energizing solenoid valve connects port 84 with atmospheric air port allowing air to enter chamber B, releasing the printing platen assembly, and as the pressure in chamber B approaches atmospheric, the contacts of vacuum switch 81 open connecting ports 97 and 98 of solenoid valve in readiness for the start of the next printing operation.

The present improved vacuum photographic printing apparatus utilizes a relatively thin printing glass and yet obtains perfect all-over contact by the rolling or squeegee action or" the upper platen assembly on the glass without subjecting it to undue strain, because of the novel construction and operation of the diaphragm, first adhering to the platen as the platen and glass bow toward each other at the center, and then leaving the upper platen under atmospheric pressure to contact the printing glass with a squeegee action from the center out. This novel construction also accomplishes the squeegee action without requiring substantial bull: in the cover as would be the case if an inflated pneumatic rubber platen were used, and yet provides apparatus using a ditfusion light source for obtaining high definition pictures of large size.

What is claimed is:

1. Vacuum photographic printing apparatus including a cabinet containing a diffusion light source, a contact printing glass mounted in the cabinet in the path of the light source, a cover hinged on the cabinet for registering with and substantially completely covering the printing glass, a flexible seal molding on the under side of the cover extending around its periphery, a resilient diaphragm completely covering the under side of the cover and the seal molding, a platen supported at its periphery on the cover above the diaphragm and substantially coextensive with the diaphragm within the seal molding, means clamping said diaphragm to said platen at its periphery forming a continuous marginal channel between the diaphragm and the printing glass, a first vacuum orifice extending through the central portion of the platen and communicating with the space between the platen and the diaphragm, and a second vacuum orifice extending through the platen and diaphragm and communicating with said marginal channel, and means for exhausting air simultaneously through both orifices until a predetermined amount of vacuum is obtained therein and for then automatically opening said first orifice to the atmosphere while continuing to exhaust air through the second orifice.

2 Vacuum photographic printing apparatus including a cabinet containing a difiusion light source, a contact printing glass mounted in the cabinet in the path of the light source, a cover hinged on the cabinet for registering with and substantially completely covering the printing glass, a flexible seal molding on the under side of the cover extending around its periphery, a resilient diaphragm completely covering the under side of the cover and the seal molding, a platen supported at its periphery on the cover above the diaphragm and substantially cextensive with the diaphragm within the seal molding, means clamping said diaphragm to said platen at its periphery forming a continuous marginal channel between the diaphragm and the printing glass, a diilusion screen between the platen and the diaphragm and having its outer edges within said clamping means, a first vacuum orifice extending through the central portion of the platen and communicating with the space between the platen and the diaphragm, and a second vacuum orifice extending through the platen and diaphragm and communicating with said marginal channel, and means for ex hausting air simultaneously through both orifices until a predetermined amount of vacuum is obtained therein and for then automatically opening said first orifice to the atmosphere while continuing to exhaust air through the second orifice.

3. Vacuum photographic printing apparatus including a cabinet containing a diiiusion light source, a horizontal contact printing glass mounted in the top of the cabinet over the light source, a co er hinged on the cabinet and having a peripheral frame for registering with the periphery of said printing glass, a flexible seal molding secured to and extending around the under side of the frame, a platen located within and extending continuously across the frame and supported at its outer periphery on the frame, a resilient diaphragm completely covering the under side of the platen and the seal molding, means spaced inwardly of said seal molding clamping the diaphragm to the periphery of the platen and forming a continuous marginal channel between the diaphragm and printing glass inside of the seal molding, a first vacuum orifice extendin through the central portion of the platen and communicating with the space between the platen and the diaphragm, and a second vacuum orifice extending through the platen and diaphragm and communicating with said marginal channel, and means for exhausting air simultaneously through both orifices until a predetermined amount of vacuum is obtained therein and for then automatically opening said first orifice to the atmosphere While continuing to exhaust air through the second orifice.

4-. Vacuum photographic printing apparatus including a cabinet containing a difiusion light source, a horizontal contact printing glass mounted in the top or the cabinet over the light source, a cover hinged on the cabinet and having a peripheral frame tor registering with the periphery of said printing glass, a flexible seal molding se cured to and extending around the under side of the frame, a lat-c located within and extending continuously across the frame and supported at its outer periphery on the frame, a resilient diaphragm completely covering the under side of the platen and the seal molding, means spaced inwardly of said seal molding clamping the diaphragm to the periphery of the platen and forming a continuous marginal channel between the diaphragm printin glass inside or" the seal molding, a difiusion screen between platen and the diaphragm and having its outer edges spaced inwardly from the marginal channel. a first vacuum orifice extending through the central portion of the platen and communicating with the space between the platen and the diaphragm, and a second vacuum orifice extending through the platen and dia into d phragm and communicating with said marginal channel, and means for exhausting air simultaneously through both orifices until a predetermined amount of vacuum is obtained therein and for then automatically opening said first orifice to the atmosphere while continuing to exhaust air through the second orifice.

5. Vacuum photographic printing apparatus including a cabinet containing a difiusion light source, a timer motor in electrical circuit with said light source, a horizontal contact printing glass mounted in the top of the cabinet over the light source, a cover hinged on the cabinet for registering with and substantially completely covering the printing glass, a flexible seal molding on the under side of the cover extending around its periphery,

a resilient diaphragm completely covering the under side of the cover and the seal molding, a platen supported at ohery on the cover above the diaphragm and substantially coextensive with the diaphragm inside of the seal molding, means clamping said diaphragm to the outer periphery of the platen forming a continuous marginal channel between the diaphragm and the printing glass, a first vacuum orifice extending through the central portion of the platen and communicating with the space between the platen and the diaphragm, a second vacuum orifice extending through the diaphragm and platen and communicating with said marginal channel, means for exhausting air from said orifices, and a third vacuum orifice extending through cover of said platen and communicating with the space between the platen and the diaphragm, and a vacuum-o erated s itch controlling the diffusion light source and timer motor circuit and operatively connected to said third vacuum orifice.

6. Vacuum photogra hic printing apparatus including a cabinet containing a di sion light source, a timer motor in electrical circuit with said light source, a horizontal contact printing glass mounted in the top of the cabinet over the light source, a cover hinged on the cabinet for registering with and substantially completely covering the printing glass, a flexible seal molding on the under side of the cover extending around its periphery, a resilient diaphragm completely covering the under side of the cover and the seal molding, a platen supported at its periphery on the cover above the diaphragm and substantially coextensive with the diaphragm inside of the seal molding, means clamping said diaphragm to the outer periphery of the platen forming a continuous marginal channel between the di phragm and the printing glass, a diffusion screen located between the platen and the diaphragm and having its outer edges spaced inwardly of said marginal channel, a first vacuum orifice extending through the central portion of the platen and communicating with the space between the platen and the diaphragm, a second vacuum orifice extending through the diaphragm and platen and communicating with said marginal channel, means for exhausting air from said orifices, and a third vacuum orifice extending through one cover of said platen and communicating with the space between the platen and the diaphragm, and a vacuumoperated switch controlling the dittusion light source and timer motor circuit and operatively connected to said third vacuum orifice.

7. Vacuum photographic printing apparatus including a cabinet containing a diffusion light source, a contact printing glass mounted in the cabinet in the path of the light source, a cover hinged on the cabinet for registering with and substantially completely covering the printing glass, a flexible seal molding around the under side of the periphery of the cover, a resilient diaphragm completely covering the under side of the cover and the seal molding, a platen supported at its periphery above the diaphragm and substantially coextensive therewith spaced inwardly of the seal molding, means clamping the diaphragm to the platen and forming a continuous marginal channel between the diaphragm. and the printing glass, means for exhausting air simultaneously from the marginal channel and from the space between the dia 1,246,620 phragm and the platen and for then automatically open- 1,688,059 ing said space to the atmosphere while continuing to ex- 2,170,622 haust air from the channel, and a switch operated on a vacuum decrease connected to said space between the 5 diaphragm and the platen for controlling the light source. 8191623 654,421 Soltniann July 24, 1900 10 Levy Nov. 13, 1917 Sack Oct. 15, 1928 Sussin Aug. 22,'1939 FOREIGN PATENTS Germany Nov. 5, 1951 

